Deep Excavation Design
Stability of the temporary excavation between Soldier Piles in Unsaturated Residual Granites in Sandton CBD
F.H van der Merwe and J.H. Engelbrecht. October 2019.
AYGE Conference, Cape Town.
The design of multi-anchored tieback soldier pile walls in Sandton is typically based on either empirical methods or two-dimensional finite element modelling, ignoring the effects of matric suction in unsaturated residual granites. The designer, however, often relies on previous experience in a similar subsurface profile rather than established theory, to assess the ability of the soil to arch between soldier piles. Using experience rather than a sound theoretical basis for design could potentially be problematic. Excavations typically proceed in intervals between 1.5m and 2.5m before a reinforced shotcrete liner is applied. This differs from the way in which timber lagging is typically installed in smaller excavation lifts in the USA. In this study a typical Sandton residual granite profile is considered, and a matric suction profile estimated.
The newly constructed clinic resembles a mini hospital with 18 spacious consulting rooms, a pharmacy, an emergency stabilisation unit, counselling rooms, a group room for ARV treatments and TB therapy, a testing facility and antenatal care. The vegetable garden and children’s play area only add to the charm of the new clinic.
Measures have also been taken to ensure that there are no excuses to turn patients away. A 48 000 litre water reserve tank stands in the front of the building to ensure the clinic does not run out of water, and solar panels and generators will ensure that there is always electricity.
By the time Florida Clinic is completed next month, it will be the perfect place for the rapidly growing Ward 70 community (and surrounding communities) to visit for their health needs, and will therefore also take a lot of pressure off the other government clinics in the Roodepoort area.
Source:Roodepoort Record https://roodepoortrecord.co.za
GaGE Consulting were responsible for geotechnical investigations and design of retaining walls on the project.